Photodissociation is the dominant destruction pathway for small molecules in a number of astrophysical environments, including photon-dominated regions (PDRs) in the diffuse interstellar medium and at the surfaces of protoplanetary disks. Carbon monosulfide (CS) is perhaps the most important species involved in the sulfur chemistry network in PDRs and disks, and is often used as a tracer of the C/O ratio. However, its photodissociation rate is essentially unknown owing to a lack of laboratory and theoretical data. Here, we present new ab initio calculations of highly excited electronic states of CS at the MRCI+Q/aug-cc-pV(5+d)Z level of theory. Photodissociation cross sections are calculated by solving the coupled Schrödinger equation, which includes a treatment of nonadiabatic and spin-orbit interactions among the electronic states. Our calculations are in excellent agreement with the available experimental spectroscopic data, including for predissociative states. We find that the dominant contribution to the CS photodissociation rate under the standard interstellar radiation field comes from predissociation via the B 1Σ+ and C 1Σ+ states, and that the total rate is approximately 3 times greater than that derived from the cross sections available in the Leiden photodissociation/photoionization database. We will also present progress on high-resolution experimental measurements of CS photodissociation through the B and C states using two-color vacuum ultraviolet spectroscopy coupled with velocity map imaging.

Vacuum ultraviolet photodissociation of CS

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.